05받은 바이트 수로 진행률을 계산하는 프로그레시브 로드 바

<main class="stage">
<div class="pvb is-demo" id="pvbRoot" tabindex="0" aria-label="다운로드 진행 막대, 스페이스로 정지·화살표로 속도 조절">
  <p class="pvb__title">문서.pdf</p>
  <div class="pvb__track" id="pvbTrack">
    <div class="pvb__fill" id="pvbFill"></div>
  </div>
  <div class="pvb__row">
    <span class="pvb__pct" id="pvbPct">0%</span>
    <span class="pvb__bytes" id="pvbBytes">0 / 0 KB</span>
  </div>
  <p class="pvb__pages" id="pvbPages">남은 페이지 12</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-ink);

.pvb {
  position: relative;
  width: min(84vw, calc(140vh - 11.2vw));
  margin: 0 auto;
  border-radius: $r-card;
  background: $subject-cream;
  box-shadow: $shadow-raised;
  padding: $sp-5 $sp-4;
  box-sizing: border-box;
  outline: none;
}

.pvb__title {
  margin: 0 0 $sp-3;
  font-size: 13px;
  font-weight: 700;
  color: $subject-ink;
}

.pvb__track {
  position: relative;
  height: 10px;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .12);
  overflow: hidden;
}

.pvb__fill {
  position: absolute;
  inset: 0 auto 0 0;
  width: 0%;
  border-radius: $r-pill;
  background: linear-gradient(90deg, $subject-blue, $subject-blue-light);
}

.pvb__row {
  display: flex;
  justify-content: space-between;
  margin-top: $sp-2;
  font-size: 11px;
  color: rgba(23, 20, 26, .6);
}

.pvb__pct { font-weight: 700; color: $subject-ink; }

.pvb__pages {
  margin: $sp-2 0 0;
  font-size: 11px;
  color: rgba(23, 20, 26, .55);
}

@media (max-width: 340px) {
  .pvb { padding: $sp-4 $sp-3; }
}

@media (prefers-reduced-motion: reduce) {
  .pvb__fill { transition: none; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.pvb {
  position: relative;
  width: min(84vw, 140vh - 11.2vw);
  margin: 0 auto;
  border-radius: 16px;
  background: #fff7e6;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  padding: 20px 16px;
  box-sizing: border-box;
  outline: none;
}

.pvb__title {
  margin: 0 0 12px;
  font-size: 13px;
  font-weight: 700;
  color: #17141a;
}

.pvb__track {
  position: relative;
  height: 10px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.12);
  overflow: hidden;
}

.pvb__fill {
  position: absolute;
  inset: 0 auto 0 0;
  width: 0%;
  border-radius: 999px;
  background: linear-gradient(90deg, #2f6df6, #5b8cf8);
}

.pvb__row {
  display: flex;
  justify-content: space-between;
  margin-top: 8px;
  font-size: 11px;
  color: rgba(23, 20, 26, 0.6);
}

.pvb__pct {
  font-weight: 700;
  color: #17141a;
}

.pvb__pages {
  margin: 8px 0 0;
  font-size: 11px;
  color: rgba(23, 20, 26, 0.55);
}

@media (max-width: 340px) {
  .pvb {
    padding: 16px 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .pvb__fill {
    transition: none;
  }
}

(function () {
  // 기법: 초당 전송 속도를 사인 합성 곡선(결정적, 시드 없이도 매 실행 동일)으로 만들어
  // 프레임마다 받은 바이트 수에 더한다. 받은 바이트 / 전체 바이트로 진행률을 매 순간
  // 다시 계산해 막대 너비와 남은 페이지 수(전체 페이지 중 아직 못 받은 비율)를 함께 갱신한다.
  var root = document.getElementById('pvbRoot');
  var fill = document.getElementById('pvbFill');
  var pctEl = document.getElementById('pvbPct');
  var bytesEl = document.getElementById('pvbBytes');
  var pagesEl = document.getElementById('pvbPages');

  var TOTAL_BYTES = 480000;
  var TOTAL_PAGES = 12;
  var HOLD_MS = 260;

  function speedCurve(tSec) {
    // 결정적 의사 지터: 세 개의 사인을 더해 "빨라졌다 느려졌다" 하는 네트워크 느낌
    var base = 210000;
    var v = base
      + 90000 * Math.sin(tSec * 2.3)
      + 40000 * Math.sin(tSec * 5.1 + 1.4)
      + 20000 * Math.sin(tSec * 9.7 + 0.6);
    return Math.max(30000, v);
  }

  var received = 0, speedMul = 1, paused = false, holdT = 0;

  function render() {
    var ratio = Math.max(0, Math.min(1, received / TOTAL_BYTES));
    fill.style.width = (ratio * 100).toFixed(1) + '%';
    pctEl.textContent = Math.round(ratio * 100) + '%';
    bytesEl.textContent = Math.round(received / 1000) + ' / ' + Math.round(TOTAL_BYTES / 1000) + ' KB';
    var remain = Math.ceil((1 - ratio) * TOTAL_PAGES);
    pagesEl.textContent = ratio >= 1 ? '전체 페이지 준비 완료' : ('남은 페이지 ' + remain);
  }

  var userActive = false;
  function markActive() { if (!userActive) { userActive = true; root.classList.remove('is-demo'); } }

  root.addEventListener('keydown', function (e) {
    if (e.key === ' ' || e.key === 'Spacebar') { e.preventDefault(); markActive(); paused = !paused; }
    else if (e.key === 'ArrowUp') { e.preventDefault(); markActive(); speedMul = Math.min(4, speedMul * 1.5); }
    else if (e.key === 'ArrowDown') { e.preventDefault(); markActive(); speedMul = Math.max(0.25, speedMul / 1.5); }
  });
  root.addEventListener('click', function () { markActive(); paused = !paused; });

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) { root.classList.remove('is-demo'); userActive = true; received = TOTAL_BYTES * 0.5; render(); }

  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!paused) {
      if (received >= TOTAL_BYTES) {
        holdT += dt;
        if (holdT >= HOLD_MS) { received = 0; holdT = 0; }
      } else {
        var sec = ts / 1000;
        received = Math.min(TOTAL_BYTES, received + speedCurve(sec) * speedMul * (dt / 1000));
      }
      render();
    }
    requestAnimationFrame(tick);
  }
  render();
  requestAnimationFrame(tick);
})();

import { useEffect, useRef } from "react";
import styles from "./PdfViewerByteProgressLoadBar.module.scss";

type KeyEvt = { key: string; preventDefault(): void };

export default function PdfViewerByteProgressLoadBar() {
  const rootRef = useRef<HTMLDivElement>(null);
  const fillRef = useRef<HTMLDivElement>(null);
  const pctRef = useRef<HTMLSpanElement>(null);
  const bytesRef = useRef<HTMLSpanElement>(null);
  const pagesRef = useRef<HTMLParagraphElement>(null);

  useEffect(() => {
    const root = rootRef.current, fill = fillRef.current, pctEl = pctRef.current;
    const bytesEl = bytesRef.current, pagesEl = pagesRef.current;
    if (!root || !fill || !pctEl || !bytesEl || !pagesEl) return;

    const TOTAL_BYTES = 480000;
    const TOTAL_PAGES = 12;
    const HOLD_MS = 260;

    function speedCurve(tSec: number) {
      const base = 210000;
      const v = base
        + 90000 * Math.sin(tSec * 2.3)
        + 40000 * Math.sin(tSec * 5.1 + 1.4)
        + 20000 * Math.sin(tSec * 9.7 + 0.6);
      return Math.max(30000, v);
    }

    let received = 0, speedMul = 1, paused = false, holdT = 0;
    function render() {
      const ratio = Math.max(0, Math.min(1, received / TOTAL_BYTES));
      fill!.style.width = (ratio * 100).toFixed(1) + "%";
      pctEl!.textContent = Math.round(ratio * 100) + "%";
      bytesEl!.textContent = Math.round(received / 1000) + " / " + Math.round(TOTAL_BYTES / 1000) + " KB";
      const remain = Math.ceil((1 - ratio) * TOTAL_PAGES);
      pagesEl!.textContent = ratio >= 1 ? "전체 페이지 준비 완료" : ("남은 페이지 " + remain);
    }

    let userActive = false;
    function markActive() { if (!userActive) { userActive = true; root!.classList.remove("is-demo"); } }

    function onKeydown(e: KeyEvt) {
      if (e.key === " " || e.key === "Spacebar") { e.preventDefault(); markActive(); paused = !paused; }
      else if (e.key === "ArrowUp") { e.preventDefault(); markActive(); speedMul = Math.min(4, speedMul * 1.5); }
      else if (e.key === "ArrowDown") { e.preventDefault(); markActive(); speedMul = Math.max(0.25, speedMul / 1.5); }
    }
    function onClick() { markActive(); paused = !paused; }
    root.addEventListener("keydown", onKeydown as unknown as EventListener);
    root.addEventListener("click", onClick);

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) { root.classList.remove("is-demo"); userActive = true; received = TOTAL_BYTES * 0.5; render(); }

    let lastTs: number | null = null, raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = Math.min(ts - lastTs, 48);
      lastTs = ts;
      if (!paused) {
        if (received >= TOTAL_BYTES) {
          holdT += dt;
          if (holdT >= HOLD_MS) { received = 0; holdT = 0; }
        } else {
          const sec = ts / 1000;
          received = Math.min(TOTAL_BYTES, received + speedCurve(sec) * speedMul * (dt / 1000));
        }
        render();
      }
      raf = requestAnimationFrame(tick);
    }
    render();
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      root.removeEventListener("keydown", onKeydown as unknown as EventListener);
      root.removeEventListener("click", onClick);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.pvb} is-demo`} ref={rootRef} tabIndex={0} aria-label="다운로드 진행 막대, 스페이스로 정지·화살표로 속도 조절">
        <p className={styles.title}>문서.pdf</p>
        <div className={styles.track}>
          <div className={styles.fill} ref={fillRef} />
        </div>
        <div className={styles.row}>
          <span className={styles.pct} ref={pctRef}>0%</span>
          <span className={styles.bytesTxt} ref={bytesRef}>0 / 0 KB</span>
        </div>
        <p className={styles.pages} ref={pagesRef}>남은 페이지 12</p>
      </div>
    </main>
  );
}